Poor retention of the filler in the paper results in increased contents of the filler in circulation waters of the papermaking process, which may cause problems in the process. Use of chemical retention aids, such as c-PAM (cationic polyacrylamide) has its limits too. cPAM is an aggressive flocculation polymer that may easily lead to formation problems in form of strong flocculation.
Another problem related to the large filler proportions is the weakening of the mechanical properties of the paper product, because the fillers interfere with the bonds between the fibres which create the structural integrity of the paper product mainly by means of hydrogen bonds between cellulose molecules. Neither does cPAM have any strengthening or densifying effect on paper properties.
Both the poor retention of the filler and weakened mechanical properties of the paper product are due to poor fiber-filler bond in the fibrous network.